Scotch malt whisky production involves several stages, the most important of which is arguably the maturation process by which new-make whisky is matured for several years in wooden casks.
Whisky is typically ˜60% water, ˜40% ethanol (and ˜0.1% other constituents), when it is casked, but during the maturation process (which typically takes ten to twenty years) a proportion of the fluid volume in the cask is lost to the atmosphere. This is affectionately referred to in the trade as the “angels' share”.
The angels' share is, in Scotland, typically around 2% volume per annum. Elsewhere in the world the loss can be as high as 5% per annum. Some whisky producers may have tens of millions of whisky casks undergoing maturation at any one time so these losses are clearly significant. In fact, the angels' share is reported to cost on the order of 10-15% of the production cost.
Wines, cognacs, armagnacs, sherries, ports, whiskeys (e.g. Bourbon) and beers may also be matured in barrels (as may balsamic vinegar), and the angels' share loss problem is also known to affect these maturation processes (to lesser or greater extents). This is therefore a wide reaching problem, and a solution that at least partially solves the problem will provide major economic benefits.
Experiments have been conducted in which whisky casks have been shrink-wrapped in order to prevent such fluid loss. While fluid loss is eliminated (or significantly reduced) by such processes there is a corresponding elimination (or significant reduction) in air ingress which is believed to negatively affect the maturation process and hence the taste of the final product.
The inventors have previously developed an alternative method and apparatus to reduce fluid loss from a cask during a maturation process as described in detail within international patent application number PCT/GB2012/051621. The apparatus comprises a vessel employed to sealably enclose the cask and thus provide an expansion volume around the cask in order to provide a means for accumulating the vapour leakage. A light source and detector based monitoring system can then be employed to determine a relative transmission of the light through the expansion volume and thus provided a measure of the fluid loss from the cask.
In practice it is not always convenient, or indeed possible, to deploy the described vessels. Furthermore, once deployed the rate of fluid loss is low and so it can be a long time before sufficient fluid loss has accumulated within the expansion volume in order to be detected by the monitoring system. These issues are particularly true for vessels designed to accommodate multiple casks.
It is recognised in the present invention that considerable advantage is to be gained in the provision of an apparatus and method capable of quickly and accurately monitoring the lost volume of product from a maturation process.
It is therefore an object of an aspect of the present invention to obviate or at least mitigate the foregoing disadvantages of the maturation monitoring apparatus and methods known in the art.